ABSTRACT: Low back pain (LBP) is a major public health issue. There is lack of research on this disorder afecting urban cleaning workers. A cross-sectional study was conducted to describe the prevalence of LBP, occupational and extra-occupational characteristics, as well as associated factors in these workers. A census was performed with 624 workers in Salvador, Brazil, using a questionnaire administered by an interviewer in 2010. Cases of LBP were deined by reported symptoms of pain in the previous 12 months, lasting more than a week or with monthly minimum frequency, which led to restrictions at work or to seeking medical attention, or in cases when respondents had a severity score ≥ 3 on a numerical scale from 0 to 5. Physical demands at work were measured on a numerical 6-point scale with 14 variables. Psychosocial demands were measured using the Job Content Questionnaire. Sociodemographic factors, lifestyle habits and domestic work were evaluated. Multiple logistic regression (LR) was used to identify factors associated with LBP, for which the prevalence was 37.0%. Among them, 62.8% of workers felt pain in the last 7 days. LBP was associated with longer working hours, lexion and trunk rotation, psychosocial demands, working directly in collection and low schooling. Dynamic work (walking, running) served as a protective factor. It was concluded that many workers develop their activity at the presence of pain. The results emphasize the need for preventive measures through multifactorial approach encompassing adaptations in physical environment and changes in work organization.
Keywords: Low back pain. Epidemiology. Urban cleaning. Cumulative trauma disorders. Human engineering. Musculoskeletal system.
Heavy physical work and low back pain:
the reality in urban cleaning
Trabalho físico pesado e dor lombar: a realidade na limpeza urbana
Silvana Maria Santos PataroI, Rita de Cássia Pereira FernandesI
IFaculdade de Medicina da Bahia da Universidade Federal da Bahia – Salvador (BA), Brasil.
Corresponding author: Silvana Maria Santos Pataro. Faculdade de Medicina da Bahia. Praça XV de novembro, s/nº, Largo do Terreiro de Jesus, CEP: 40025-010, Salvador, BA, Brasil. E-mail: silpataro1@hotmail.com
Conlict of interests:nothing to declare – Financial support:none.
INTRODUCTION
Low back pain is one of the major public health issues in several industrialized and developing countries, not only due to its high prevalence and incidence, but also because of the labor incapacity it generates, the intensive use of health services it causes and the number of missed working days. Therefore, it is an important cause for the concession of disability insurance1,2.
In many countries, the urban cleaning activity is performed manually, thus exposing the worker to a series of occupational risks, especially those related to physical work overload, as in the case of musculoskeletal impairment3,4. The role of the physical load caused by
frequent trunk lexion and rotation, lifting and/or carrying load, whole body vibration and heavy physical work in the occurrence of low back pain has been widely documented. In the past few years, studies have focused on the psychosocial demands at the workplace5.
Epidemiological studies in diferent occupational categories have been conducted in diferent countries, however, there is a gap when it comes to studies that approach the prevalence of low back pain with clear case deinition, especially those performed with active individuals. Inconclusive epidemiological studies are also due to the lack of contrast required in the exposure to risk factors, which makes it diicult to determine the associations
in more homogeneous occupational groups. Besides, the inadequate control of confusing factors and the inaccurate categorizations of exposure may mask the results6.
Therefore, an epidemiological study was conducted with the objectives of estimating the prevalence of low back pain, and specifying its frequency, severity and duration of pain, besides the sociodemographic, occupational, extra-occupational characteristics and the factors associated with low back pain in a population of urban cleaning workers.
METHODS
This is a cross-sectional study involving a population of 657 urban cleaning workers (UCW) in Salvador. It was chosen to conduct a census with the maintenance and operation staf from the company that provides the service to the city.
A questionnaire was used for data collection, and direct measurements of weight and height were taken in the beginning, during and at the end of the work shift in a reserved place. The used questionnaire, elaborated by Fernandes7, was adapted for the population
of UCW, considering their own characteristics. This questionnaire was composed by the following items: sociodemographic aspects; current and former occupational history; habit of smoking; intake of alcohol; use of medications; presence of comorbidities; practice of physical exercises and sports; household chores; questions about musculoskeletal symptoms; and issues related to physical and psychosocial demands at work.
The questionnaire incorporates the ampliied version of the Nordic Musculoskeletal Questionnaire (NMQ)8, which is an instrument that assesses the presence of pain or discomfort
in the previous 12 months in anatomic regions of the musculoskeletal system, as well as its severity, duration and frequency.
Cases of low-back Musculoskeletal Disorders (MSD) were deined as the sensation of pain in the past 12 months lasting over one week or minimum monthly frequency, not caused by acute lesion, associated with one or more of the following criteria: level of severity ≥ 3 in a
scale from 0 to 5, with anchors on the extremities (no discomfort to unbearable discomfort); search for medical care due to the problem; absence at work (oicial or not); changing work due to health restrictions8,9. Cases of low-back pain referred to complaints about pain in this
region in the past 12 months, without the aforementioned severity criteria. Besides the low-back region, the questionnaire included the following body segments: ingers, hands, ists, forearms, elbows, neck, shoulders, upper back, hips and thighs, knees, legs and ankles. The prevalence of musculoskeletal pain referred only to the presence of pain in one or more of the cited regions in the previous 12 months and, in the case of MSD, pain in the respective body segment that met the aforementioned criteria.
The questionnaire investigated the physical demand at work by means of questions answered by the workers as to frequency, duration or intensity of exposure, in a scale from 0 to 5, with anchors on the extremities, about the work posture, repetitive movements and handling loads.
The psychosocial demands at work were measured by the incorporation of the Job Content Questionnaire ( JCQ)10,11. In the analysis, the scores were obtained for psychological
demand, control social support and dissatisfaction at work.
For measures of weight and height, obtained with the objective of calculating the body mass index, a portable scale and a stadiometer were used as instruments.
In the statistical approach of data, the prevalence of low-back MSD was analyzed (dependent variable), as well as the means and their respective standard-deviations for most of the independent variables and the percentage of exposure for the other variables. After the descriptive stage, a multivariate logistic regression analysis was conducted using the Epi-Info 6.04 and the R statistical software, respectively.
All of the independent variables in this study were dichotomized. The schooling variable was stratiied as lower than complete high school and higher or equal to complete high school. Marital status was identiied as married or living together and single or living alone; the presence of children was analyzed as children aged less than two years old and older than two years old or no children; body mass index (BMI) was considered as overweight or obesity and normal or low weight.
The intake of alcohol at least once a week was adopted as the cutof point. With regard to physical activity, individuals were asked about what they did while not working in the company or at home. “Sedentary” subjects (exposure) were those who reported activities such as reading the newspaper or a magazine, watching television and studying. The report of competitive sports activity or actions like running, doing gymnastics, walking, bike riding, swimming, ishing and gardening were considered as non-exposure (“active”). The variables overtime, smoking and vibration were dichotomized as to the presence or not of the exposure registration.
Variables related to physical demands were summarized into three indexes. The irst one refers to the posture in trunk lexion and rotation. The second one refers to dynamic work and includes the variables walking, running, standing up, crouching, and jumping from diferent levels. In both cases, median was established as the cutof point. The third index, for handling load, was created from the variables lifting, pushing and pulling loads, with the adoption of the cutof point above the irst quartile, since it would better discriminate this variable. The sitting work was stratiied by mean.
The high exposure for psychosocial demand was deined as high psychological demand, low control and low social support10. The registration of at least two of these criteria
For occupation, performing the activity of waste collection was considered as exposure, and not performing this activity, as non-exposure. The other variables were dichotomized by the mean.
The pre-selection of independent variables to enter the multivariate logistic regression model was based on the biological plausibility criteria of the associations, as well as on the univariate logistic regressions, considering a p-value of 0.25 in the likelihood ratio test for the signiicance of the coeicient13.
The backward model was adopted for the selection of variables. In this exploratory study, α equals to 0.16 was used to enter the model. The choice of a value between 0.15 and
0.20 for the inclusion of variables in this stage is highly recommended, considering that the choice of more rigorous signiicance levels can exclude important variables from the model13.
Since it is a census, and knowing that the methods of statistical inference apply only to the analysis of results obtained from a random sample14,15, even though the intermediate
stages of the logistic regression model required the adoption of alpha values for the selection and permanence of variables, the inal results of the model were presented only through the measure of association, without considering conidence intervals.
This study was approved by the Research Ethics Committee of Hospital São Rafael, protocol n. 48/09.
RESULTS
From the total of 657 workers, there was a 5.02% loss, which corresponded to losses and workers on leave with disability insurance, who were not found for interview. The total population of the study was then comprised of 624 workers, all of whom were male. The 624 workers held the following occupations: 367 waste collectors, 118 drivers, 84 cleaning agents and 55 maintenance workers.
The prevalence of pain or discomfort in the past 12 months and of cases of MSD, both considering any segments of the body, was of 77.4 and 62.8%, respectively, in this category. For low-back pain and low-back MSD, according to the speciicity criteria that were previously deined, prevalence of 45.5 and 37.0% was found, respectively, superior to the ones found for pain and MSD in other body segments (Table 1). Among the cases of low-back MDS, it was observed that 62,8% of the workers had pain in the last 7 days.
The mean age of the interviewed workers was of 33.9 years old. Out of these, 55.3% were black, 72.0% were married, 18.0% had children younger than 2 years old and 63.1% had not completed high school. The mean of weekly hours destined to household chores was of 4.9 (Table 2).
With regard to occupational aspects, about 96.5% of the workers performed their activities in a ixed shift, and 85.1% did overtime. The total work time was of 19.1 years, and the mean time in the company was of 56.6 months. The mean weekly working hours was of 54.8 hours (Table 2).
The variables for physical demands are presented in Table 3. The work standing up or performing dynamic activities walking, running and jumping from diferent levels, as well as postures in trunk lexion and rotation, conducting repetitive movements with the hands and raising the arms above the shoulders are frequent among collectors. Besides, a higher exposure to handling load was registered among them when compared to the other occupations. Among drivers, the exposure to the work sitting down and to whole body vibration is frequent, being the latter also referred by collectors due to the truck movements.
The scores for psychosocial demands are presented in Table 4. A higher score was observed for the psychological demand among collectors. A higher control over work was registered among drivers and maintenance workers, and more social support was seen among cleaning agents. The latter, as well as collectors, had higher scores for dissatisfaction at work.
#Refers to pain in the last 12 months, lasting a week or more or minimum monthly rate associated with one or more of
the following items: severity ≥ 3 on a scale of 0 to 5; seeking medical attention, absence from work, job change due to health restriction.
Body segment
Pain in the last
12 months UCW#
n % n %
In some body region (upper limbs, lower limbs or spine) 483 77.4 392 62.8
Upper distal extremities (elbow, forearm, ist or hand) 169 27.1 127 20.4
Neck, shoulder or upper back 237 38.0 176 28.2
Neck 98 15.7 66 10.6
Shoulder 152 24.4 111 17.8
Upper back 89 14.3 69 11.1
Elbow or forearm 62 9.9 46 7.4
Fist or hand 132 21.2 96 15.4
Leg, ankle or foot 159 25.5 118 18.9
Thigh or knee 165 26.4 124 19.9
Spinal region 284 45.5 231 37.0
Table 2. Sociodemographic characteristic, lifestyle habits, occupational and extra-occupational
characteristics of urban cleaning workers. Salvador, BA, Brazil, 2011.
Sociodemographic and life habits variables Total populationn = 624 (%)
Age (years, mean ± SD) 33.9 ± 8.3
Ethnicity
White 46 (7.4)
Black 344 (55.3)
Yellow 10 (1.6)
Brown 212 (34.1)
Indigenous 10 (1.6)
Marital status
Married or living together 448 (72.0)
Single or living alone 174 (28.0)
Children
< 2 years old 110 (18.0)
≥ 2 years old 368 (60.3)
No children 132 (21.6)
Schooling
≥ complete high school 229 (36.9)
< complete high school 392 (63.1)
Alcohol intake
≥ Once /week 356 (57.3)
< Once/week 265 (42.7)
Smoking
Yes 91 (14.6)
No 532 (85.4)
BMI
Low weight 33 (5.3)
Normal 322 (51.8)
Overweight 204 (32.8)
Table 5 reveals the results of the multivariate analysis. It is observed that low back pain was 1.65 times more frequent among those who were mostly exposed to trunk lexion and rotation. Those who performed more dynamic work were more protected for low back pain in relation to those who did not perform those activities. Workers exposed to a higher psychosocial demand had 1.63 times more low back pain than the ones who were not exposed. It was also observed that workers who had more time of activity inside the company and with lower schooling had more low back pain in comparison to those with less time and higher schooling. Waste collectors had 1.66 times more low back pain than the ones who were not collectors (Table 5).
DISCUSSION
The prevalence of low back MSD among UCWs was high, given the severity criteria adopted in this study. The high prevalence of pain in the past seven days was also noticed among the cases of low back MSD, which demonstrates that many workers perform their work activities at the presence of considerable symptoms. The results of most studies about the prevalence of musculoskeletal symptoms, especially in the low back segment, show the presence of pain in the last 12 months, without adopting severity criteria, thus inding moderate to high values for the prevalence of low back pain in diferent populations16,17.
Occupational and extra-occupational variables Total populationn = 624 (%)
Work regime
Fixed shit 602 (96.5)
Rotating shit 18 (2.9)
Administrative hours 4 (0.6)
Overtime
Yes 531 (85.1)
No 93 (14.9)
Total time of formal + informal work (years, mean ± SD) 19.1 ± 9.1
Time at the company (months, mean ± SD) 56.6 ± 53.0
Working hours at the company in the past week (mean ± SD) 54.8 ± 13.8
Hours of household chores in the past week (mean ± SD) 4.9 ± 6.7
Table 2. Continuation.
Variables of physical demand Collectors Drivers Cleaning
agents Maintenance
(0 = never 5 = all the time) (mean ± SD)
Sitting position 0.3 ± 0.7 4.6 ± 0.8 0.3 ± 0.9 1.0 ± 1.3
Standing position 4.8 ± 0.7 0.6 ± 0.9 4.6 ± 1.1 4.1 ± 1.2
Walking 3.2 ± 1.8 0.3 ± 0.6 4.3 ± 1.3 3.8 ± 1.5
Running 4.5 ± 1.3 0.0 ± 0.1 1.2 ± 1.7 0.6 ± 1.1
Jumping from diferent levels 4.4 ± 1.3 1.6 ± 1.4 1.6 ± 1.7 2.4 ± 1.9
Crouch position 3.7 ± 1.5 0.1 ± 0.2 2.4 ± 1.6 2.8 ± 1.4
Trunk leaning forward 4.0 ± 1.3 1.8 ± 1.5 3.4 ± 1.3 2.7 ± 1.4
Rotated trunk 4.1 ± 1.3 2.0 ± 1.7 3.0 ± 1.6 2.3 ± 1.3
Arms lited above the shoulder 3.8 ± 1.6 0.8 ± 1.2 2.9 ± 1.7 2.8 ± 1.6
Repetitive movements with the hands 4.8 ± 0.7 4.6 ± 0.9 4.5 ± 1.0 4.5 ± 0.8
Handling load
Liting 4.3 ± 1.1 0.1 ± 0.5 3.2 ± 1.6 3.0 ± 1.6
Pushing 3.9 ± 1.4 0.2 ± 0.8 2.7 ± 1.8 2.9 ± 1.6
Pulling 3.7 ± 1.5 0.1 ± 0.6 2.9 ± 1.9 2.8 ± 1.8
Whole body vibration
Yes 222 (66.1%) 79 (73.1%) 29 (35.4%) 22 (46.8%)
No 114 (33.9%) 29 (26.9%) 53 (64.6%) 25 (53.2%)
Table 3. Physical demands at work by occupation in urban cleaning workers. Salvador, BA, Brazil, 2011.
In this study, the inclusion of questions related to the severity of cases enabled to reduce the classiication error of the disease with the purpose of an epidemiological analysis and improved the speciicity of the evaluation18.
Studies about the prevalence of low back MSD among UCWs are rare not only in Brazil, but also in other countries. A cross-sectional study conducted with workers of this category found a 45.6% prevalence of low back pain, which is similar to this study (45.5%). With regard to musculoskeletal pain in one or more of the nine deined regions of the body in the past 12 months, studies observed prevalence of 6517 and 54.7%19, which were inferior
to those in this investigation.
industry20, and 28.9% for workers in the plastic industry9, and these results are inferior to
the ones found in this study.
The mean age found among the UCWs in this study was compatible with the mean of other studies in the same category17,21, thus showing the relatively Young proile of this category,
which can relect on physical demands of the developed tasks, leading to overload for the body. The low schooling was observed in this category, which is in accordance with data referring to the population from Bahia (only 3.8% are have 15 or more schooling years). Besides, little more than half of the assessed population was composed of black people, who were considered as the ones with less schooling years when compared to other ethnicities22.
Other studies with UCWs had similar results concerning schooling17,23. According to Ilário25,
the UCWs represent disqualiied work force, whose occupational background is usually
Table 4. Distribution of scores by occupation for psychological demands, control, social support
and job dissatisfaction in urban cleaning workers. Salvador, BA, Brazil, 2011.
Occupation Psychosocial demand
Total population (n = 624)
(mean ± SD)
Psychological
demand Control supportSocial Dissatisfaction
Collectors 40.0 ± 6.2 58.1 ± 9.2 23.4 ± 4.3 0.36 ± 0.26
Drivers 36.7 ± 5.8 64.3 ± 9.6 23.1 ± 4.4 0.20 ± 0.22
Cleaning agents 34.3 ± 5.9 59.2 ± 10.4 24.2 ± 4.2 0.37 ± 0.28
Maintenance workers 32.0 ± 7.0 66.7 ± 9.1 22.8 ± 4.0 0.29 ± 0.24
Limit values for psychological demand = 48 – 12; control at work = 96 – 24; social support = 32 – 8; job dissatisfaction = 1 – 0.
Table 5. Multivariate Analysis. Association between low back pain and variables in the inal model
in urban cleaning workers. Salvador, BA, Brazil, 2011 (n = 582).
Variables RP
Time of work at the company 1.65
Trunk lexion-rotation 1.65
Dynamic work 0.59
Psychosocial demand 1.63
Occupation 1.66
Schooling 1.47
related to construction or other sort of manual labor. These data relect the low schooling of this category and the diiculty and the diiculty to enter the work market in other ields. The possible consequence for that is the submission to diicult conditions in this activities and the low interlocution with the management for better work conditions.
The intake of alcohol among these workers is very high21,23,24. This study demonstrated
high frequency of alcohol intake at least once a week, and this result is compatible with other studies in the same category, which indicate the stressful activity of public waste collection as the precursor of the onset of alcohol intake, calling the attention to the risk of alcoholism among waste collectors23,24.
A low frequency was found with regard to the habit of smoking in this study, when compared to others in this category17,24. The prevalence of smoking can be related to the
socioeconomic status, being more common among workers who perform manual work and those who are unemployed24,25.
Another investigated characteristic was the body mass index, which proved to be normal for more than half of the workers, which can relect the dynamic character of the urban cleaning activity.
Among the occupational characteristics, it was observed that the total work time demonstrates, based on the mean age of these individuals, the early insertion in the work market, and many of them began in the informal market, in little qualiied activities. Besides, the mean time of 4.7 years in the company may relect the high workforce turnover in this category24.
The number of working hours per week among the UCWs is above the predicted working hours by the Federal Constitution of 1988 and by the labor legislation. Even though the workday determined by the company is of eight hours, the workers cannot fulill the predicted working hours, given the volume of work. This is even more evident by the frequency of overtime reported by the workers. It is known that, due to the characteristics of production, the variability of working conditions and the means to execute the task, that the daily workload is extrapolated, even if paid as overtime3.
The mean hours spent in household chores in the previous week was similar to that found among men in the plastic industry26. The little workload found in this study is probably due
to the sociocultural construction of a behavior in which the household chore is seen mostly as a female activity, and also because of the hard working hours outside of the house, which is a characteristic of this category.
The high exposure to physical demands, such as handling load and trunk postures in lexion and rotation, is compatible with the one found among nursing workers27 and superior
to that registered among workers in the plastic industry26 using the same instrument.
The self-registration of repetitive movements was high for all of the UCWs, which is a similar result to the one found in the aforementioned studies in other categories26,27. However,
based on a repetitive task concept, which is characterized by work cycles smaller that lasts less than 30 seconds, or fundamental cycles constituting more than 50% of the total work cycle28, an activity that is much more globally dynamic than repetitive is observed in this
question, mostly interpreted as repetitive gestures of distal extremities and others, such as a work situation that is repeated on working days.
With regard to psychosocial demands, high scores were observed for the psychological demand and social support among cleaning workers, higher than the ones found in industry26
and in the health sector27. This relects the high demand and the accelerated rhythm found
in this service, as well as the essentially collective work, especially inside the collection and cleaning teams. In these activities, there is the need for group cohesion, such as collective competence, so that they can perform their work and administrate situations of task variability29,30. More work dissatisfaction at work and less control over it were registered
among collectors and cleaning agents. In the collection service, drivers have more autonomy and decision making abilities over the activity3.
Physical and psychosocial demands at work were positively associated with cases of low back pain in this population. Besides these, other occupational factors, such as time of work in the company and being a waste collector were also positively associated. Among the non-occupational variables, the low schooling remained associated with low back pain.
The activity of waste collection is essentially manual3, which requires from the worker
constant trunk lexion and rotation movements in the manipulation of waste volumes. Yang et al.31 found 2.16 times more low back pain among collection workers than among
the ones in other activities in the same company, when adjusted by age, gender, education, smoking and time in the company, which corroborates the result of this study, in which low back pain was 1.66 times higher in this occupation when compared to the others.
The movement of throwing garbage bags during collection generates high shear strength over the low back region4. Besides, extreme lexion postures and the torsion of the trunk
that are present in some activities related to handling waste are described in literature as being associated with low back pain complaints5,6, and proved by the results in this study.
Risk estimates for frequent lexion and rotation movements range from 1.3 and 8.1, and this interval is higher than the one found for load lifting (1.1 to 3.5) in a literature review5.
Excessive posture desensitizes mechanoreceptors, which are in charge of neuromotor control, with consequent loss of the relex contraction of stabilizing muscles and the increased load over the spine32.
Among the UCWs in this study, it was observed that the dynamic occupational work functioned as a protective factor for low back pain. This inding seems to be supported by literature, since the static activity is more damaging to the spine than the dynamic activity. The postural variation enables better disc nutrition, thus preventing its degeneration. Besides, physical aptitude components, such as muscular resistance, which are a characteristic of the dynamic activity, are pointed out as being important protective factors33.
Consistent results in diferent study designs have been found for the relationship between low back pain and psychosocial aspects of work34,35. The psychosocial demand has been
Some possible explanations of the relationship between psychosocial aspects and low back pain are the fact that the psychosocial characteristics of work may increase psychological tension, and, therefore, muscular activity and excretion of hormones, which contributes with the development or worsening of the symptoms5,34. Psychosocial aspects can also
decrease the pain threshold, thus causing increased report of symptoms34. Likewise, low
back pain can afect the perception about work or the way it is performed.
Other variables associated with low back pain were time of work in the company and schooling. The time of exposure to this activity contributes with low back pain, possibly due to the effect of cumulative trauma, which is very discussed in MSD studies5. As to schooling, no associations were found in studies with UCWs17.
Some studies that reveal such an association usually do not present adjusted estimates for the physical work load6.
This study points out to the need for preventive and control measures concerning low back pain at work, through a multifactorial approach that includes adaptation in the physical environment and changes in aspects related to work organization. To provide an adequate physical environment, with proper equipment, tools and technology for the performance of tasks can contribute to reduce the need for extreme movements or the adoption of anomalous trunk postures. It is also important to introduce strategies that promote the expression of capacities, autonomy over the work chore, temporal management of the activity and group support in the context of organizational management.
REFERENCES
1. Hoogendoorn WE, Bongers PM, de Vet HC, Ariens GAM, van Mechelen W, Bouter LM. High physical work load and job satisfaction increase the risk of sickness absence due to low back pain: results of a prospective cohort study. Occup Environ Med 2002; 59(5): 323-8.
2. Soucy I, Truchon M, Côté D. Work-related factors contributing to chronic disability in low back pain. Work 2006; 26(3): 313-26.
3. Camada IMO, Pataro SM, Fernandes RC. Heavy physical work under time pressure: the garbage collection service- a case study. Work 2012; 41(Suppl 1): 462-69.
4. Poulsen OM, Breum NO, Ebbehøj N, Hansen AM, Ivens UI, van Lelieveld D et al. Collection of domestic waste. Review of occupational health problems and their possible causes. Sci Total Environ 1995; 170(1-2): 1-19.
5. National Research Council/Institute of Medicine [NRC & IM]. Musculoskeletal disorders and the workplace: low back and upper extremities. Washington DC: National Academy Press; 2001.
6. Burdorf A, Sorock G. Positive and negative evidence of risk factors for back disorders. Scand J Work Environ Health 1997; 23(4): 243-56.
7. Fernandes RCP. Distúrbios músculo-esqueléticos e trabalho industrial [tese de doutorado]. Salvador: Instituto de Saúde Coletiva da Universidade Federal da Bahia; 2004.
8. Kuorinka I, Forcier L. Work related musculoskeletal disorders (WMSDs): a reference book for prevention. London: Taylor & Francis; 1995.
9. Fernandes RC, Carvalho FM, Assunção AA. Prevalence of musculoskeletal disorders among plastics industry workers. Cad Saúde Pública 2011; 27(1): 78-86.
10. Karasek R. Job Content Instrument: Questionnaire and User’s guide. Massachusetts: University of Massachusetts Amhers; 1985.
12. Devereux JJ, Vlachonikolis IG, Buckle PW. Epidemiological study to investigate potential interaction between physical and psychosocial factors at work that may increase the risk of symptoms of musculoskeletal disorder of the neck and upper limb. Occup Environ Med 2002; 59(4): 269-77.
13. Hosmer DW, Lemeshow S. Applied logistic regression. Wiley Interscience: New York; 2000.
14. Silvany Neto AM. Bioestatística sem segredos. Edição do autor: Salvador; 2008.
15. Conceição MJ. Leitura Crítica dos Dados Estatísticos em Trabalhos Cientíicos. Ver Bras Anestesiol 2008; 58(3): 260-6.
16. Hartvigsen J, Bakketeig LS, Leboeuf-Y C, Engberg M, Lauritzen T. The association between physical workload and low back pain clouded by the “healthy worker” efect: population-based cross-sectional and 5-year prospective questionnaire study. Spine (Phila Pa 1976) 2001; 26(16): 1788-92.
17. Mehrdad R, Majlessi-Nasr M, Aminian O, Shariian AS, Malekahmadi F. Musculoskeletal disorders among municipal solid waste workers. Acta Medica Iranica 2008; 46(3): 233-38.
18. Baron S, Hales T, Hurrel J. Evaluation of symptom surveys for occupational musculoskeletal disorders. Am J Ind Med 1996; 29(6): 609-17.
19. Oliveira MG. Características organizacionais e acidentes ocupacionais em empresas de limpeza urbana de Salvador-BA [tese de doutorado]. Salvador: Instituto de Saúde Coletiva da Universidade Federal da Bahia; 2008.
20. Ijzelenberg W, Burdorf A. Risk factors for musculoskeletal symptoms and ensuing health care use and sick leave. Spine (Phila Pa 1976) 2005; 30(13): 1550-6.
21. Miglioransa MH, Rosa LC, Perin C, Ramos GZ, Fossati GF, Stein A. Estudo epidemiológico dos coletores de lixo seletivo. Rev Bras Saúde Ocup 2003; 28(107-018): 19-28.
22. Instituto Brasileiro de Geograia e Estatística [Internet]. Síntese de Indicadores Sociais 2010. Disponível em: http:// www.ibge.gov.br. (Acessado em 26 de setembro de 2010).
23. Dos Santos Mabuchi A, de Oliveira DF, de Lima MP, da Conceição MB, Fernandes H. The use of alcohol by workers of the garbage collection service. Rev Lat Am Enfermagem 2007; 15(3): 446-52.
24. Ilário E. Estudo de morbidade em coletores de lixo de um grande centro urbano. Rev Bras Saúde Ocup 1989; 17(66): 7-13.
25. Palmer KT, Syddall HE, Cooper C, Coggon D. Smoking and musculoskeletal disorders: indings from a British national survey. Ann Rheum Dis 2003; 62(1): 33-6.
26. Fernandes RCP, Assunção AA, Silvany Neto AM, Carvalho FM. Muskuloskeletal disorders among workers in plastic manufacturing plants. Rev Bras Epidemiol 2010; 13(1): 11-20.
27. Ribeiro NF, Fernandes RCP, Solla DJF, Junior ACS, Junior ASS. Prevalência de disturbios osteomusculares relacionados ao trabalho em prof issionais de enfermagem. Rev Bras Epidemiol 2012; 15(2): 429-38.
28. Kilbom A. Assessment of physical exposure in relation to work-related musculoskeletal disorders-what information can be obtained from systematic observations? Scand J Work Environ Health 1994; 20: 30-45.
29. Vasconcelos RC, Lima FPA, Camarotto JA, Abreu ACMS, Coutinho Filho AOS. Aspectos de complexidade do trabalho de coletores de lixo domiciliar: a gestão da variabilidade do trabalho na rua. Gest Prod São Carlos 2008; 15(2): 407-19.
30. Santos MCO, Lima FPA, Murta EP, Motta GMV. Desregulamentação do trabalho e desregulação da atividade: o caso da terceirização da limpeza urbana e o trabalho dos garis. Produção 2009; 19(1): 202-13.
31. Yang CH, Chang WT, Chuang HY, Tsai SS, Wu TN, Sung FC. Adverse health efects among household waste collectors in Taiwan. Environ Res 2001; 85(3): 195-99.
32. Pope MH, Goh KL, Magnusson ML. Spine ergonomics. Annu Rev Biomed Eng 2002; 4: 49-68.
33. Toscano JJO, Egypto EP. A inluência do sedentarismo na prevalência de lombalgia. Rev Bras Med Esporte 2001; 7(4): 132-7.
34. Hoogendoorn WE, Bongers PM, de Vet HCW, Houtman ILD, Ariens GAM, van Mechelen W, et al. Psychosocial work characteristics and psychological strain in relation to low-back pain. Scand J Work Environ Health 2001; 27(4): 258-67.
35. Fernandes RCP, Carvalho FM, Assunção AA, Silvany Neto AM. Interactions between physical and psychosocial demands of work associated to low back pain. Rev Saúde Públ 2009; 43(2): 326-34.
Received on: 01/12/2012
Final version presented on: 05/16/2012
Brazilian Journal of Epidemiology 2014;17(1):18, 20, 22, 24, 26, 28 e 30 DOI: 10.1590/1809-4503201400010003
Article: Heavy physical work and low back pain: the reality in urban cleaning
On pages 18, 20, 22, 24, 26, 28 e 30, where it reads: PATARO, S.M.S. ET AL.
Should read:
